This is a tricky question. Thoughtfully explaining why you left your last job will tell the employer a lot about your personality. You've likely left, or are thinking about leaving, your last sales job because it wasn't a good fit or because you didn't like the work environment, the pay, or management. Though they may be truthful answers, all of these reasons carry a negative connotation and will pull down the mood of the interview. First, state something positive about your last job. Maybe you learned a lot or enjoyed the people you worked with. Then, shift the focus of why you left by talking about what you're looking for in your next job that your past job didn't have. This might be more responsibility, relocation, or a different company culture. This will present your past work experience in a positive light and compliment the position for which you're interviewing.